On the server side, if you don't plan to use the old, user-mode NFS daemon, you'll need to compile NFS server support into the kernel (``NFS server support,'' a.k.a. knfsd or
CONFIG_NFSD). If you plan to use the older RARP protocol to assign the client an IP address, RARP support in the kernel of the server is probably a good idea. (You must have it if you will boot via RARP without kernel parameters.) On the other hand, it doesn't help you if the client isn't on the same subnet as the server.
The kernel for the workstation needs the following settings, as a minimum:
CONFIG_NFS_FS). Note that there is no need for ext2 support.
For dynamically assigned IP numbers, you'll also need to select one or more of these kernel options:
If the workstation will be booted without kernel parameters, you need also to set the root device to 0:255. Do this by creating a dummy device file with
mknod /dev/nfsroot b 0 255. After having created such a device file, you can set root device of the kernel image with
rdev <kernel-image> /dev/nfsroot. [NOTE: Modern kernels recognize
root=/dev/nfs as a command-line argument; for consistency and/or compatibility, it may be better to use
/dev/nfs as the device name instead of
Warning: while these instruction might work for you, they are by no means sensefull in a production environment. For a better way to set up a root filesystem for the clients, see the NFS-Root-Client mini-HOWTO by Ofer Maor
After having decided where to place the root tree, create it with (e.g.)
mkdir -p <directory> and
tar cClf / - | tar xpCf <directory> -.
If you boot your kernel without LILO, then the rootdir has to be
/tftpboot/<IP-address>. If you don't like it, you can change it in the top Makefile in the kernel sources, look for a line like:
NFS_ROOT = -DNFS_ROOT="\"/tftpboot/%s\"" If you change this, you have to recompile the kernel.
Now trim the unneeded files, and check the /etc/rc.d scripts. Some important points:
Export the root dir to the workstation. The basic idea is to edit
/etc/exports to include a line similar to one of the following:
/path/on/server/to/nfs_root <client-IP-number>(rw,no_root_squash,no_all_squash) <2nd-client-IP-number>(rw,no_root_squash,no_all_squash)
For example, a DHCP client receiving an IP address on a class C subnet would need an exports entry similar to this:
no_root_squash parameter allows the superuser (root) to be treated as such by the NFS server; otherwise root will be remapped to nobody and will generally be unable to do anything useful with the filesystem. The
no_all_squash parameter is similar but applies to non-root users. See the
exports(5) man page for details.
You will have to notify the NFS server after making any changes to the exports file. Under Red Hat this can easily be done by typing
/etc/rc.d/init.d/nfs stop; /etc/rc.d/init.d/nfs start. On other systems, a simple
/etc/rc.d/init.d/nfs restart or even
exportfs -a may suffice, while on older machines running the user-mode NFS daemon you may actually need to
killall -HUP rpc.mountd; killall -HUP rpc.nfsd. (Do not
killall -HUP rpc.portmap, however!)
You may also need to edit
/etc/hosts.deny if tcp_wrappers are installed. In particular, if the remote system (client) gets RPC: connection refused errors,
/etc/hosts.deny probably contains
portmap: ALL or
ALL: ALL. To enable the client to use the server's portmapper, add a corresponding line to
portmap: <client-IP-number> portmap: <2nd-client-IP-number> portmap: <client-IP-network>/<client-IP-netmask>
There is no need to restart anything in this case. You can check by running
rpcinfo -p on the NFS server and
rpcinfo -p NFS-server on a Linux client within the allowed range; the RPC services listed by both should match.
In case of problems, check
/var/log/syslog for errors (for example, run
tail -f /var/log/messages /var/log/syslog and then try booting the client), and check your man pages (exports, exportfs, portmap, etc.). As a last resort, a reboot of the NFS server may help, but that's a borderline Microsoftism...
Set up the RARP somewhere on the net. If you boot without a nfsroot parameter, the RARP server has to be the NFS server. Usually this will be the NFS server. To do this, you will need to run a kernel with RARP support.
To do this, execute (and install it somewhere in
/etc/rc.d of the server!):
/sbin/rarp -s <ip-addr> <hardware-addr>
is the IP address of the workstation, and
is the ethernet address of the network card of the workstation.
/sbin/rarp -s 22.214.171.124 00:00:c0:47:10:12
You can also use a symbolic name instead of the IP address, as long the server is able to find out the IP address. (/etc/hosts or DNS lookups)
For BOOTP setup you need to edit
/etc/bootptab. Please consult the bootpd(8) and bootptab(5) man pages.
There is no need for the DHCP server to be the same as the NFS server, and in most cases, a DHCP server will already be set up. If one is not, however, consult the DHCP mini-HOWTO for further help.
I don't know the hardware address! How can I find it out?